全文获取类型
收费全文 | 1003篇 |
免费 | 136篇 |
国内免费 | 61篇 |
专业分类
电工技术 | 132篇 |
综合类 | 61篇 |
化学工业 | 255篇 |
金属工艺 | 61篇 |
机械仪表 | 63篇 |
建筑科学 | 50篇 |
矿业工程 | 9篇 |
能源动力 | 67篇 |
轻工业 | 90篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
武器工业 | 1篇 |
无线电 | 86篇 |
一般工业技术 | 101篇 |
冶金工业 | 31篇 |
原子能技术 | 2篇 |
自动化技术 | 183篇 |
出版年
2024年 | 3篇 |
2023年 | 120篇 |
2022年 | 84篇 |
2021年 | 53篇 |
2020年 | 70篇 |
2019年 | 38篇 |
2018年 | 35篇 |
2017年 | 27篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 61篇 |
2013年 | 74篇 |
2012年 | 110篇 |
2011年 | 91篇 |
2010年 | 60篇 |
2009年 | 61篇 |
2008年 | 32篇 |
2007年 | 84篇 |
2006年 | 76篇 |
2005年 | 19篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有1200条查询结果,搜索用时 15 毫秒
1.
《Journal of the European Ceramic Society》2021,41(15):7868-7877
In this work, 0.5TRPO•0.5Gd2Zr2O7 ceramic with an average grain size of only ∼15 nm was prepared by a high pressure (5 GPa/520 °C) sintering method. Phase evolutions and microstructure changes of the as-fabricated super nano and micron-grained ceramics under a high-dose displacement damage induced by 300 keV Kr2+ ions were investigated. The results show that the super nano-grained ceramic has low degree of amorphization, obvious grain growth (2–3 times in grain size) and big Kr bubbles (10–68 nm) formation after irradiation. The micron-grained ceramic was severely amorphized after irradiation and many microcracks were formed parallel to its surface. The formation mechanism of Kr bubbles in the super nano-grained ceramic is on account of grain boundary diffusion and migration induced by the accumulation of the injecting Kr ions and irradiation defects. Nevertheless, microcracks formed in the micron-grained sample are caused by the accumulation of Kr atoms. 相似文献
2.
《Journal of the European Ceramic Society》2020,40(15):5475-5482
The lead-free Ba0.53Sr0.47TiO3 (BST) thin films buffered with La0.67Sr0.33MnO3 (LSMO) bottom electrode of different thicknesses were fabricated by pulsed laser deposition method on a (001) SrTiO3 substrate. It was found that the roughness of electrode decreases and substrate stress relaxes gradually with the increase of LSMO thickness, which is beneficial for weakening local high electric field and achieving higher Eb. Therefore, the recoverable energy density (Wrec) of BST films can be greatly improved up to 67.3 %, that is, from 30.6 J/cm3 for the LSMO thickness of 30 nm up to 51.2 J/cm3 for the LSMO thickness of 140 nm after optimizing the LSMO thickness. Furthermore, the thin film capacitor with a 140 nm LSMO bottom electrode shows an outstanding thermal stability from 20 °C to 160 °C and superior fatigue resistance after 108 electrical cycles with only a slightly decrease of Wrec below 1.6 % and 3.7 %, respectively. Our work demonstrates that optimizing bottom electrodes thickness is a promising way for enhancing energy storage properties of thin-film capacitors. 相似文献
3.
文章论述了色织亚麻金线提花织物的特点,介绍了在生产实践中采用低张力络筒和低速度整经等工艺技术,开发出的产品滑爽、挺括、透气,立体感强,是一种良好的装饰和服装用纺织流行面料。 相似文献
4.
5.
《Journal of the European Ceramic Society》2006,26(6):967-980
Through a study of Ni–YSZ interfaces it is shown that time-of-flight-secondary ion mass spectrometry (TOF-SIMS) is a powerful and convenient tool for the analysis of ultra thin layers of segregated material at the interfaces and on free surfaces. Two different types of Ni, “pure Ni” (99.995% Ni) and “impure Ni” (99.8% Ni) were investigated. The contact areas on the YSZ and areas outside the contacts were examined with XPS and TOF-SIMS. The impure nickel causes a relatively larger amount of impurities to accumulate at the contact area, e.g. oxides of Mn, Ti, Si and Na. Some impurities migrate to the area outside the contact area. Even though on a larger scale the impurities seem to be homogeneously distributed, detailed analyses in and outside the contact area show the presence of impurity particles, and that the surface species are inhomogeneously distributed amongst the different grains. The extremely low detection limit, the small probe depth, the image capability, and the ease of elemental identification make TOF-SIMS an obvious choice as an analytical tool for studying segregation phenomena at metal–ceramic interfaces such as Ni–YSZ interfaces. XPS, being a quantitative technique, was used as a complementary technique to TOF-SIMS, which is not directly a quantitative technique. 相似文献
6.
Sustainable and cleaner manufacturing systems have found broad applications in industrial processes, especially aerospace, automotive and power generation. Conventional manufacturing methods are highly unsustainable regarding carbon emissions, energy consumption, material wastage, costly shipment and complex supply management. Besides, during global COVID-19 pandemic, advanced fabrication and management strategies were extremely required to fulfill the shortfall of basic and medical emergency supplies. Three-dimensional printing (3DP) reduces global energy consumption and CO2 emissions related to industrial manufacturing. Various renewable energy harvesting mechanisms utilizing solar, wind, tidal and human potential have been fabricated through additive manufacturing. 3D printing aided the manufacturing companies in combating the deficiencies of medical healthcare devices for patients and professionals globally. In this regard, 3D printed medical face shields, respiratory masks, personal protective equipment, PLA-based recyclable air filtration masks, additively manufactured ideal tissue models and new information technology (IT) based rapid manufacturing are some significant contributions of 3DP. Furthermore, a bibliometric study of 3D printing research was conducted in CiteSpace. The most influential keywords and latest research frontiers were found and the 3DP knowledge was categorized into 10 diverse research themes. The potential challenges incurred by AM industry during the pandemic were categorized in terms of design, safety, manufacturing, certification and legal issues. Significantly, this study highlights the versatile role of 3DP in battle against COVID-19 pandemic and provides up-to-date research frontiers, leading the readers to focus on the current hurdles encountered by AM industry, henceforth conduct further investigations to enhance 3DP technology. 相似文献
7.
陈俊健 《网络安全技术与应用》2012,(8):15-17
存储系统会有成百上千的存储设备和大量的数据。其中有相当部分敏感数据需要加密存储,然而现有的存储系统只能对整个文件进行加密,而不能对文件某一部分进行加密。尽管其实现方法比较简单,但它会导致系统额外的开销并且极大的影响系统性能。本文提出了存储系统的一种文件细粒度加密方案,它可以充分利用分布式存储内在的特性,有效地利用元数据信息对文件内多个任意大小的数据块进行加密。用户还可以根据数据块的保密级别对不同的数据块定义不同的加密算法以满足需要。对于广泛存在的视频、地图、档案等大文件实现不同粒度加密策略,可减少文件中不必要的数据加密操作,极大提高存储系统的性能。 相似文献
8.
可变频率变压器(VFT)是一种能连接异步电网的新型灵活交流输电系统设备,其可传输功率的容量是重要的性能指标。针对传统控制策略未考虑转差率增大可能导致转子绕组超过额定容量的问题,对不同的转差率和定子无功功率情况下定子有功功率最大值进行研究;详细研究了采用串联变换器的VFT系统运行特性;对不同转差率进行了详细的工况分析。推导出最优定子无功功率给定值与转差率、额定视在功率和实际吸收无功功率之间的数学关系,并提出了VFT的最大功率传输(MPT)控制策略;通过硬件在环实验平台验证提出的MPT控制策略的有效性。实验结果表明,所提MPT控制策略能有效提高VFT的可传输功率,实现VFT的最大功率传输。 相似文献
9.
《中国稀土学报(英文版)》2022,40(8):1255-1263
CeO2/g-C3N4 photocatalysts have attracted tremendous attention in the photocatalytic degradation of organic pollutants. The design and construction of highly active CeO2/g-C3N4 photocatalysts without harsh conditions are still challenging. Herein, highly dispersed CeO2–x nanoparticles with rich oxygen vacancies were successfully precipitated on the surface of g-C3N4 under mild conditions. The fabricated CeO2–x/g-C3N4 exhibits remarkable activity and stability for photocatalytic degradation of MO pollutant. The optimal rate constant of MO degradation over CeO2–x/g-C3N4 is about 0.031 min?1, which is three times higher than that of g-C3N4. A negligible activity decrease is observed after three cycling runs. The enhanced catalytic performance can be ascribed to the excellent dispersion of CeO2–x with rich oxygen vacancies that benefit O2 adsorption and visible light absorption. In addition, the proper band alignment between CeO2–x and g-C3N4 is conducive to the highly efficient separation of photogenerated electron–hole pairs. 相似文献
10.